The invention relates generally to the field of automatically and wirelessly collecting data from items being tracked, and more particularly, to a system and method of detecting and identifying items more accurately with multiple scans.
There are a number of ways of identifying and tracking items including visually, optically (bar coding, for example), magnetically, RFID, weighing, and others. Where an automatic system for tracking is desired, RFID is a candidate since identification data may be obtained wirelessly. RFID tags have decreased in cost, which has made them even more attractive for such an application.
Radio-frequency identification (“RFID”) is the use of electromagnetic energy (“EM energy”) to stimulate a responsive device (known as an RFID “tag” or transponder) to identify itself and in some cases, provide additionally stored data. RFID tags typically include a semiconductor device having a memory, circuitry (collectively the “circuitry element”), and one or more conductive traces that form an antenna. Typically, RFID tags act as transponders, providing information stored in the semiconductor device memory of the circuitry element in response to an RF interrogation signal received from a reader, also referred to as an interrogator. Some RFID tags include security measures, such as passwords and/or encryption. Many RFID tags also permit information to be written or stored in the semiconductor memory via an RF signal.
RFID tags may be incorporated into or attached to items to be tracked. In some cases, the tag may be attached to the outside of an item with adhesive, tape, or other means and in other cases, the tag may be inserted within the item, such as being included in the packaging, located within the container of the item, or sewn into a garment. The RFID tags are manufactured with an identification number which is typically a simple serial number of a few bytes with a check digit attached. This identification number is incorporated into the tag during manufacture. The user cannot alter this serial/identification number and manufacturers guarantee that each serial number is used only once. This configuration represents the low cost end of the technology in that the RFID tag is read-only and it responds to an interrogation signal only with its identification number. Typically, the tag continuously responds with its identification number. Data transmission to the tag is not possible. These tags are very low cost and are produced in enormous quantities.
Such read-only RFID tags typically are permanently attached to an item to be tracked and, once attached, the serial number of the tag is associated with its host item in a computer data base. For example, a particular type of medicine may be contained in hundreds or thousands of small vials. Upon manufacture, or receipt of the vials at a health care institution, an RFID tag is attached to each vial. Each vial with its permanently attached RFID tag will be checked into the data base of the health care institution upon receipt. The RFID identification number may be associated in the data base with the type of medicine, size of the dose in the vial, and perhaps other information such as the expiration date of the medicine. Thereafter, when the RFID tag of a vial is interrogated and its identification number read, the data base of the health care institution can match that identification number with its stored data about the vial. The contents of the vial can then be determined as well as any other characteristics that have been stored in the data base. This system requires that the institution maintain a comprehensive data base regarding the items in inventory rather than incorporating such data into an RFID tag.
An object of the tag is to associate it with an item throughout the item's life in a particular facility, such as a manufacturing facility, a transport vehicle, a health care facility, a storage area, or other, so that the item may be located, identified, and tracked, as it is moved. For example, knowing where certain medical items reside at all times in a health care facility can greatly facilitate locating needed medical supplies when emergencies arise. Similarly, tracking the items through the facility can assist in generating more efficient dispensing and inventory control systems as well as improving work flow in a facility. Additionally, expiration dates can be monitored and those items that are older and about to expire can be moved to the front of the line for immediate dispensing. This results in better inventory control and lowered costs.
Other RFID tags are writable and information about the item to which the RFID tag is attached can be programmed into the individual tag. While this can provide a distinct advantage when a facility's computer servers are unavailable, such tags cost more, depending on the size of the memory in the tag. Programming each one of the tags with information contained in the item to which they are attached involves further expense. As used herein, the term “item” has the same meaning as the word “article.”
RFID tags may be applied to containers or items to be tracked by the manufacturer, the receiving party, or others. In some cases where a manufacturer applies the tags to the product, the manufacturer will also supply a respective data base file that links the identification number of each of the tags to the contents of each respective item thereby “associating” the RFID tag with the product, or vial, or item, or item. That manufacturer-supplied data base can be distributed to the customer in the form of an electronic file that may easily be imported into the customer's overall data base thereby saving the customer from the expense of creating the data base.
Data base creation can also be a problem from an efficiency aspect. It has been noted that errors are often made when creating the data base manually at a health care facility. Numbers can be transposed, left off, or incorrectly entered, as can expiration dates, and other important information. Receiving the data base file from the manufacturer usually results in far fewer errors or none at all. Additionally, the data base file from the manufacturer may be conveniently available through the Internet, which involves none of the handling problems that arise from time to time with physical media. Problems such as the digital versatile disc (“DVD”) on which the data base has been written cannot be read, or is missing from the shipment, are avoided. Furthermore, making the data base available as a downloadable file over the Internet allows the manufacturer to make last minutes changes as the products are being shipped out the door.
Many RFID tags used today are passive in that they do not have a battery or other autonomous power supply and instead, must rely on the interrogating energy provided by an RFID reader to provide power to activate the tag. Passive RFID tags require an electromagnetic field of energy of a certain frequency range and certain minimum intensity in order to achieve activation of the tag and transmission of its stored data. Another choice is an active RFID tag; however, such tags require an accompanying battery to provide power to activate the tag, thus increasing the expense of the tag and making them undesirable for use in a large number of applications.
Depending on the requirements of the RFID tag application, such as the physical size of the items to be identified, their location, and the ability to reach them easily, tags may need to be read from a short distance or a long distance by an RFID reader. Such distances may vary from a few centimeters to ten or more meters. Additionally, in the U.S. and in other countries, the frequency range within which such tags are permitted to operate is limited. As an example, lower frequency bands, such as 125 KHz and 13.56 MHz, may be used for RFID tags in some applications. At this frequency range, the electromagnetic energy is less affected by liquids and other dielectric materials, but suffers from the limitation of a short interrogating distance. At higher frequency bands where RFID use is permitted, such as 915 MHz and 2.4 GHz, the RFID tags can be interrogated at longer distances, but they de-tune more rapidly as the material to which the tag is attached or is nearby varies. It has also been found that at these higher frequencies, closely spaced RFID tags will de-tune each other as the spacing between tags is decreased.
There are a number of common situations where the RFID tags may be located inside enclosures. Some of these enclosures may have entirely or partially metal or metallized surfaces. Examples of enclosures include metal enclosures (e.g., shipping containers), partial metal enclosures (e.g., vehicles such as airplanes, buses, trains, and ships that have a housing made from a combination of metal and other materials such as glass), and non-metal enclosures (e.g., warehouses and buildings made of wood). Examples of objects with RFID tags that may be located in these enclosures include loose items, packaged items, parcels inside warehouses, inventory items inside buildings, various goods inside retail stores, and various portable items (e.g., passenger identification cards and tickets, baggage, cargo, individual life-saving equipment such as life jackets and masks) inside vehicles, etc.
The read range (i.e., the range of the interrogation and/or response signals) of RFID tags is limited. For example, some types of passive RFID tags have a maximum range of about twelve meters, which may be attained only in ideal free space conditions with favorable antenna orientation. In a real situation, the observed tag range is often six meters and can be much less. Therefore, some of the enclosures described above may have dimensions that far exceed the read range of an individual RFID tag. Unless the RFID reader can be placed in close proximity to a target RFID tag in such an enclosure, the tag will not be activated and read. Additionally, metal surfaces of the enclosures present a serious obstacle for the RF signals that need to be exchanged between RFID readers and RFID tags, making RFID tags located behind or in close proximity to those metal surfaces difficult or impossible to detect.
In addition to the above, the detection range of the RFID systems is typically limited by signal strength to short ranges, frequently less than about thirty centimeters for 13.56 MHz systems. Therefore, portable reader units may need to be moved past a group of tagged items in order to detect all the tagged items, particularly where the tagged items are stored in a space significantly greater than the detection range of a stationary or fixed single reader antenna. Alternately, a large reader antenna with sufficient power and range to detect a larger number of tagged items may be used. However, such an antenna may be unwieldy and may increase the range of the radiated power beyond allowable limits which may cause the reader to read unrelated tags positioned outside the target enclosure causing inaccuracy. Furthermore, these reader antennas are often located in stores or other locations where space is at a premium and it is expensive and inconvenient to use such large reader antennas. In another possible solution, multiple small antennas may be used but such a configuration may be awkward to set up when space is at a premium and when wiring is preferred or required to be hidden.
In the case of medical supplies and devices, it is desirable to develop accurate tracking, inventory control systems, and dispensing systems so that RFID tagged devices and items may be located quickly should the need arise, and may be identified for other purposes, such as expiration dates. One common scenario is the restocking of an ADC. The pharmacy may prepare a large order for restocking an ADC somewhere in a health care facility and will want to track the order to be sure that it was successfully and completely delivered to the ADC. The ADC may be programmed to scan all items in its storage spaces once the doors or drawers are closed after restocking and communicate that newly-scanned inventory to the pharmacy. The pharmacy server may then compare the newly-scanned inventory in the ADC to the inventory sent to the ADC to verify that all medical items reached the ADC. If a shortage appears to exist, it would be helpful to have a system and method that can rescan the ADC storage spaces in a different manner to be sure there is a shortage, before someone must be sent to examine manually the contents of the ADC.
In the case of medical supply or dispensing cabinets used in a health care facility, a large number of medical devices and items are located closely together, such as in a plurality of drawers. Cabinets such as these are typically made of metal, which can make the use of an external RFID system for identification of the stored items difficult. In some cases, such cabinets are locked due to the presence of narcotics, expensive medication, or other medical items or apparatus within them that are subject to a high theft rate. Thus, manual identification of the cabinet contents is difficult due to the need to control access.
Providing an internal RFID system in such a cabinet can pose challenges. Where internal items can have random placement within the cabinet, the RFID system must be such that there are no “dead zones” that the RFID system is unable to reach. In general, dead zones are areas in which the level of coupling between an RFID reader antenna and an RFID tag is not adequate for the system to perform a successful read of the tag. The existence of such dead zones may be caused by orientations in which the tag and the reader antennas are in orthogonal planes. Thus, items placed in dead zones may not be detected thereby resulting in inaccurate tracking of tagged items.
It is important that RF-enabled drawers and other enclosures accurately and repeatedly identify a variety of RFID tags attached to items contained in these enclosures. The RFID tags will vary in performance (various integrated circuit (“IC”) manufacturers), antenna type (far field, near field, combination, etc.), antenna gain, location of item being tracked, susceptibility to detuning of RFID tags, and antenna design type (linear vs. circular) among other characteristics.
Additionally, it has been noted that some RFID tags underperform. That is, they are more difficult to detect, interrogate, and read under the same circumstances as other tags. Since RFID tags can be made by multiple manufacturers having varying standards and quality control, and rough handling and other environmental factors may damage tags, some of them provide problems in interrogation. Yet it is desirable that every RFID tag be read in an enclosure since the medication or other medical item to which it is attached can be important. It would be helpful to provide an RFID interrogation system that can successfully interrogate such underperforming tags.
Often in the medical field, there is a need to read a large number of tags attached to items in such an enclosure, and as mentioned above, such enclosures have limited access due to security reasons. The physical dimension of the enclosure may need to vary to accommodate a large number of items or items of different sizes and shapes. In order to obtain an accurate identification and count of such closely-located medical items or devices, a robust electromagnetic energy field must be provided at the appropriate frequency within the enclosure to surround all such stored items and devices to be sure that their tags are all are activated and read. Such medical devices may have the RFID tags attached to the outside of their containers and may be stored in various orientations with the RFID tag (and associated antenna) pointed upwards, sideways, downward, or at some other angle in a random pattern.
Additionally, where EM energy is introduced to such an enclosure for reading the RFID tags within, efficient energy transfer is of importance. Under ideal conditions, the power transfer to the enclosure can be favorable while minimizing the reflections of power within the enclosure. Where the enclosure impedance changes due to the introduction of items to the enclosure or removal of items from the enclosure, or many items are stored in one small area near each other and the items are in random orientations with very few, if any, in the desired orientation in respect to the antennas of the enclosure, or some of the RFID tags are underperforming, some or many of the tags on items within the enclosure would not be activated to identify themselves, leaving an ineffective inventory system. It is very important that all tags, and therefore medical items attached to those tags, be activated and read.
It is a goal of many health care facilities to keep the use of EM energy to a minimum, or at least contained. The use of high-power readers to locate and extract data from RFID tags is generally undesirable in health care facilities, although it may be acceptable in warehouses that are sparsely populated with workers, or in aircraft cargo holds. Radiating a broad beam of EM energy at a large area, where that EM energy may stray into adjacent, more sensitive areas, is undesirable. Efficiency in operating a reader to obtain the needed identification information from tags is an objective. Increasing the read power is not a viable option and installing beam steering or other directional technology for the antennas increases the cost and complexity.
Hence, those of skill in the art have recognized a need for an RFID tag reader system in which the efficient use of energy is made to activate and read all RFID tags in an enclosed area. A further need for the efficient use of an existing EM field in enclosures to activate and read tags disposed at random orientations has also been recognized. A further need has been recognized for an automated system to identify items stored in a metal cabinet without the need to gain access to the cabinet. Hence, those skilled in the art have recognized a need for more accurately and repeatedly identifying a large population of differing performance RFID tags attached to various size and differing material packages containing differing forms of medication, positioned in various orientations, located in differing strength RF fields, and contained in a shielded RF-enabled enclosure. Those of skill in the art have also recognized a need for an RFID tag reader system in which the efficient use of energy is made to activate and read all RFID tags in an enclosed area. A further need for establishing a robust EM field in enclosures to activate and read tags disposed at random orientations has also been recognized. A further need has been recognized for an automated system to identify items stored in a metal cabinet without the need to gain access to the cabinet. The present invention fulfills these needs and others.